I’VE seen hundreds of them, so it looked like just another gun – that is until you run your fingers over the grip, the trigger, muzzle, and think back.

Back to that terrible moment when Mark David Chapman, then 25, put his maniacal palm around that grip, his evil finger on the trigger.

It is the Charter Arms .38 Special whose muzzle spat four bullets into the body of 40-year-old John Lennon – and tears rolled across the world.

Police Lt. Mark Gallagher, head of the ballistics and forensics lab in Jamaica, Queens, where the infamous weapon is screwed into a case, says it perhaps more eloquently than can be written. “It doesn’t look as grimly intense as history has held,” the 20-year veteran was telling me. “But history shows that in a terrible way the tragedy outshines the gun.”

Gallagher was 18 and hanging out at a high school friend’s house when the news came.

“We were shocked and his [friend’s] brother, a Beatles fan, burst into tears.

“In terms of how the assassination impacted the world, that was one of the most senseless acts against a man who only wanted to do good things for the world.”

Detective Luis Fontanez, a ballistic expert at the lab and a 15-year veteran said: “The gun was made in 1964, it cost less than a hundred dollars, and sadly, in this terrible case, was very reliable.

“Law-enforcement delegations from all over the world, including China, have viewed the gun. It was, as they say, the shot heard around the world.”

Eight-hundred guns with significant links to the past are locked in the lab.

Underneath the infamous gun used against Lennon is a .44-caliber “Bulldog” special wielded by “Son of Sam” killer David Berkowitz when he declared war on New York in 1977.